1. Field of the Invention
The present invention relates to a liquid ejection print head which performs printing by ejecting a print liquid onto a printing surface of a print medium, and a tape provided with a base used for the same.
2. Description of the Related Art
A liquid ejection printing head, for example, an ink-jet printing head of a side shooter type, as shown in FIG. 11 and FIG. 12, includes a body having an ink supply portion 8 to which an ink tank (not shown) is mounted; a print element board 14 bonded to a bottom of a recessed portion 8b of the ink supply portion 8 to eject ink; and a frame member 3 having an opening 2a opposing the print element board 14 and electrically connected to each electrode of the print element board 14.
The bottom of the recessed portion 5b of the ink supply portion 8 is formed into flat shape by a metal core member 10 which is molded together with the body. At a periphery of the recessed portion 8b of the ink supply portion 8 the frame member 3 is securely attached.
At the bottom of the recessed portion 8b of the ink supply portion 8 one end of an ink supply passage 8a that introduces ink from the ink tank is opened. The cross-sectional shape of the ink supply passage 8a is shaped like a slot extending over a predetermined distance along arrays of ink ejection ports (described later).
The print element board 14 includes: a base 16 having an ink supply opening 14a communicating with an open end of the ink supply passage 8a in the ink supply portion 8 and a plurality of heaters arranged therein; and an orifice plate 12 having a plurality of ink supply branch passages 12bi for introducing ink from the ink supply opening 14a to each heater.
A plurality of heaters are arranged at both sides of the ink supply opening 14a so that they sandwich the ink supply opening 14a, at predetermined intervals in a line extending in a direction almost perpendicular to the plane of the paper in FIG. 12.
The base 16 has electrode portions 16d to which connecting portions 6a, 6b (described later) are connected at one end corresponding to each heater.
The orifice plate 12 has ink ejection ports 12ai formed at positions facing each heater in the base 16. The ink branch supply passages 12bi are provided individually for each heater in the base 16.
The print element board 14 and the frame member 3 are electrically connected to each other by tape automated bonding (TAB), for example. The frame member 3 includes a tape member 2 with an opening 2a and a conductive layer 6 bonded by an adhesive layer 4 to an entire surface of the tape member 2 on the side of the ink supply portion 8.
The tape member 2 is formed of resin, and the conductive layer 6 is formed of a metal sheet 20-30 μm in thickness. The periphery of the opening 2a encloses an area corresponding to the outer circumferential portion of the print element board 14 installed below. The conductive layer 6 has an opening 6A at a position corresponding to the opening 2a and also has a plurality of connecting portions 6a, 6b electrically connected to the corresponding electrode portions 16d of the base 16 of the print element board 14. One end of the narrow two or more connecting portions 6a, 6b extend from the periphery of the opening 6A of the conductive layer 6 to the corresponding electrode portions 16d, respectively.
A gap between the periphery of the opening 2a of the tape member 2 and the outer circumferential portion of the print element board 14 is sealed with a sealant 18. The sealant 18 covers the plurality of connecting portions 6a, 6b and encloses the print element board 14.
Arranging the print element board 14 to face the opening 2a of the tape member 2 of the frame member 3 and making electrical connections between them is performed as follows. First, the print element board 14 is located and positioned at a position relative to the opening 2a of the tape member 2 as by image processing or the like. Then, for example, one end of the connecting portions 6a, 6b are bonded to the electrode portions 16d of the base 16 of the print element board 14 as by thermocompression or ultrasonic vibration.
Then, the print element board 14 connected with the frame member 3 through the connecting portions 6a, 6b is positioned on and secured to the top surface of the ink supply portion 8. As a result, the print element board 14 is positioned relative to and reliably secured to the bottom of the recessed portion 8b of the ink supply portion 8.
When the connecting portions 6a, 6b are bonded to the electrode portions 16d of the base 16, lead forming is performed together with the bonding. Lead forming is defined as a process of correcting the amount of deformation of the connecting portions 6a, 6b to prevent the connecting portions 6a, 6b from contacting the edge of the base 16 (edge touch) as shown in FIG. 13A and thereby to prevent a short-circuit from occurring during operation.
When a gang bonder is used, the amount of lead forming is expressed based on a relative difference in height between the conductive layer 6 of the frame member 3 and the upper surface of the base 16, Lfa and Lfb, for example, as shown in FIG. 13B and FIG. 13C. Hence, the amount of lead forming for the height difference Lfa is larger than that for the height difference Lfb.
After having been subjected to a predetermined amount of lead forming, the frame member 3 and the print element board 14 coupled mutually through the connecting portions 6a, 6b are arranged at predetermined positions in the ink supply portion 8.
In the process of assembly, however, because the lead forming is performed while keeping the frame member 3 and the print element board 14 separated from the ink supply portion 8, and the print element board 14 is supported only by the elongate connecting portions 6a, 6b and the connecting portions 6a, 6b have insufficient rigidity and are easily deformed, the amount of lead forming may vary from one print head to another.
When there are variations in the amount of lead forming, the following problems occur.
First, since the variations in the amount of lead forming result in variations in the size of the gap between the periphery of the opening 2a of the tape member 2 and the outer circumferential portion of the print element board 14, the sealant 18 is not applied uniformly, resulting in defective sealing of the connecting portions 6a, 6b, which in turn may cause corrosion. To avoid such a situation, in some cases, the amount of sealant 18 applied could be increased. But this is not a good idea because it might clog the ejection openings with the sealant 18.
Second, problems arise when the frame member 3 is bonded to the ink supply portion 8.
Upon bonding the frame member 3 to the ink supply portion 8, with reference to the bonding surface of the frame member 3, the gap between the base 16 of the print element board 14 and the bottom of the recessed portion 8b can vary too, which may cause ink leakage or errors in the relative positions of the ejection openings of the orifice plate 12 with respect to the printing surface of the print medium.
Third, when the frame member 3 is bonded to the ink supply portion 8, upon bonding the frame member 3 to the ink supply portion 8, with reference to the bonding surface of the base 16, a gap is formed between the conductive layer 6 of the frame member 3 and the bonded surface of the ink supply portion 8, which may cause corrosion of the conductive layer 6 by ink.